Decaffeinated coffee can have up to 20 milligrams of caffeine (regular coffee has about 100 milligrams). Fruit tea drinks (iced or otherwise) may have caffeinated tea as part of the mix.
Non-cola sodas (unless labeled caffeine free), often have surprising levels of caffeine (even seemingly safe flavors like orange). Get to know the brands.
Any energy drink is suspect (these drinks often contain astonishing levels of caffeine).
Avoid any product (breakfast cereal, gum, mint, and others) advertised to promote alertness, give energy, or wake people up.