First, get or build a shop. Then if you need a toilet or another attraction right with the shop but no room, right click on a spot (not the entrance) and it will delete that part of the building, but it looks the same. Then put the toilet or attraction, even a shop there. It might look like its not there, but it is.

For a cool $50,000, enter your nickname as "HORZA" and start a new park. The next time you're asked for your nickname, enter it as "HORZA". From here on you can get $50,000 by pressing Ctrl-C. Also, you can hit Shift-Z for all scenery. Ctrl-Z for all the rides, and Alt-Z for all the shops.

For a megapark, enter your nickname as "DEMO", then continue. This will load up a Megapark with most of the rides but a few problems for you to fix

To get more people to buy drinks just increase the salt in the pommes fries