At first he always fibbed; there was a donation to charity, or some money slipped through the hole in his pocket, or he paid off some imaginary debts.

Later, he didn't even bother to make up anything.

He had nothing left because it had all gone into his stomach.
Madame Boche suggested to Gervaise that she go to wait for him at the shop exit.

This rarely worked though, because Coupeau's comrades would warn him and the money would disappear into his shoe or someone else's pocket.
Yes, it was their own fault if every season found them lower and lower.
But that's the sort of thing one never tells oneself, especially when one is down in the mire.

They accused their bad luck; they pretended that fate was against them.