That is only possible if you only count ingredient costs

As a business operation as a whole, it won't be so high. Should be anywhere between 10-30%. Which is the typical margin for F&B

Just remember a simple fact, if margin is really high, its easy for a competitor to undercut you.

They don't have the same costs. For sundry shops, water is an item used to draw in people so they buy more stuff. Go in for Rm1 water, also buy some bread/snacks. The renovation, equipment and staffing costs are different as well.

Generally, the RM4 is to deter you from ordering water, and to order drinks. If anything, you can use that as a benchmark as to what "profit" each drink makes. The price of the water would definietly be more than the profit of the other drinks.