The only time I ever remembering seeing my Mum really angry was due to this.
My Mum was on a diet. She went a month and a half without eating and only drinking diet lwmonade. She actually gained a bit of weight overall in waterweight and had various swelling issues due to her body reacting to the artificial sweetners (How she found out she can't use artificial sweetners. (I get my throat closing)), but anyway. What really stopped her diet that time were me and my brother.
To buy the diet lemonade was a 4 mile walk to the shop, which involved 4 miles of walking home uphill carrying the bottles. My Mum waslooking forward to her last bottle of diet lemonade... But unknown to her, my brother and I had also been enjoying it. We realized we had drunk between us most of the bottle and there was only about a third of it left.
Ah! Solution. Fill the rest with water. She won't notice as it looks the same,,, So that's what we did. Ummm.... Well.... She noticed.
The only time my brother and I had to run! My Mum was certainly not amused!
My Mum went back to eating food and abandoned the diet lemonade and she started to lose weight. It was all waterweight cause by an alergic reaction to artificial sweetners. We found out this is ver common and some artificial sweetners are mildly poisionus like saccarine, phelamine etc (Have I spelt or written that word right?) Both my Mum and I avoid artificial sweetners.
So to sum up, the bad advice is not to fill lemonade bottles with water. People do notice!