Add sugar to make more beer?

I guess this is not a beginner question, but I haven't brewed in a while, so I feel like a beginner. I probably never really got much further than a beginner stage, but I felt like I was comfortable with what I was doing.

Anyway, funny situation here. A friend of mine bought a brew kit that came with two malt syrup cans. He used one and made half a batch. He has a bigger bucket now, and I told him he can just use one can and get some more yeast and add a certain amount of sugar and make the full 6 gallons instead of just a 3 gallon batch in his bigger bucket.

However, I can't remember how to know how much sugar to add. I know that he added half the 6 oz yeast packet, so I know to pitch 6 oz of yeast.

Am I right about this? I'm pretty sure I've done it quite a few times before. I mean, some flavor may be lost, but the extra sugar will react with the yeast and make the full amount of alcohol right?

How would I calculate how much sugar to add? I can't remember what I did at all.

If you add sugar to make up for LME your gonna end up with an extremely dry beer with little flavor and possibly a high alcohol taste. It will certainly add alcohol to the beer but I can't imagine it tasting very good. If I were you, I would either buy more malt extract or just do another half batch.

Of course, I've never done this so I could be totally wrong.

Kit and Kilo beer. 1 can syrup and 1 kilo sugar.

Not ideal but, it is how it has been done.

Do you think this would make 6 gallons of beer if I added a kg of sugar?

probably not very good beer but it would probably get you drunk quickly.

Ah thanks for the quick responses everyone. I'm just gonna get another can of malt extract from the store. They aren't too expensive anyway, and I'd like him to have better tasting beer early on in his brewing career.

If you do use sugar at all use turbinado aka Sugar in the Raw.

What do you want to make Beer or prison hooch,

I think you're going to go from beer....to Malt Liquor