The side missions are optional missions you can do in the story mode. Completing side missions earns you money, so it is a good idea to at least do a few of them on your playthrough. To find side missions, look for people on the streets or in the shops with "?" above their heads, and talk to them.
There are a few guys willing to arm wrestle with you. This involves repeatedly pressing the button shown on screen until you win. Not much to say about this one.
The classic bonus game from Final Fight returns. You need to smash up the car within the time limit. However the cars in Final Fight Streetwise are considerably tougher than the one found in the original game, and require a lot of work put in to totally destroy them. In the top left corner of the screen there is a picture of the car, showing which areas have or haven't been damaged. As you damage areas of the car, parts of the picture will change from green to red to eventually no color. When there is no longer a color, it means that section of the car has been damaged enough and you can't do any more to it.
You can talk to guys who will ask if you want to play 3 card monte. The objective here is to find the card which says "WIN" on it. When the game starts, you will see this card, which will then be flipped over and shuffled around two other cards. After the shuffle stops, you get one chance to choose a card. Pick the correct card to win this.
You can find people who will want to challenge you to a game of darts (such as an old lady in Barfly). Here you need to reduce your score from 301 to exactly 0 to win. You get to throw three darts per turn, so move the cursor and then press the button to aim. A power bar will then appear, press the button at the level of power you want to throw your dart. After you've thrown three darts, your turn will be over and your opponent will have their turn. This repeats until someone wins.
There are a few side missions where you need to escort someone. As you run with them, gang members will appear and will need beating down. The person you are supposed to be protecting will have their own life gauge, if this gauge is emptied then you will fail the mission.
This is one of the stranger games: a duck shoot! Control the cursor to take aim, and then press the button to shoot. After each shot is fired, the cursor will move, so be ready to aim fast and shoot accurately. To win this game you need to shoot a certain amount of ducks.
Several side missions involve getting an item and taking it to somebody. For example, early on in the game there is some bum you can talk to, who says he's got something to say -but only if you bring him some whiskey. So go to the liquor place and buy some, then take it back and talk to the guy. Usually you won't get money for doing these side missions, instead you'll just get info.
MADAM CELESTE CARDS
Whenever you see Madam Celeste, she will ask you to try her card game. The idea here is to keep matching up two of the same card, until you complete the set. You can make a few mistakes, make too many and you'll have to start over again from scratch. When you match up all of the cards, the game will end.
Several times throughout the story you'll be required to kill some pests within a time limit. The pests are either cockroaches, rats, or both. You can stun the pests by running into them, then press either of the attack buttons to kick or stomp. The amount of pests you need to kill varies.
The slide puzzles involve trying to create a picture. You can see the picture you need to make to the bottom right of the screen. Use the analogue stick to move the pieces around.
TRASH CAN TRASHER
These games have you running around a small maze, finding and breaking trash cans. Whilst the game thinks it is a good idea to pick up the cans and throw them, it is much faster to just use normal punches on them. In the maze you'll find boxes blocking you from progressing, attack these boxes to break them. You have to smash a certain amount of cans within the time limit to complete these games.