Water should be provided at all times. However, your hamster may not actually take water every day. Please don't give your hammy milk, orange juice or the like. These may cause stomach upsets or become bad if left in the water bottle for too long. Plain water will do just fine.
Some people do give their hamsters milk, especially to nursing mothers and young.
However, we have to keep in mind that many mammals usually produce less of the enzyme needed to digest milk as they age and become weaned. My hamsters seldom drink more than 25cc of water a day. You may also have to keep in mind the weather conditions. Treat items are not necessary but can prove useful if you are to be away for a few days. Dog biscuits help promote tooth wear and you might want to try these.