Bond at 94%. Is it a good idea to buy?

Acually, you'd receive 103.125 in 6 months since the bond pays an annual coupon of 3.125%. You'd also pay about 97 for the bond based on the ASK price since you'll need the pay the amount of the coupon that's accrued to date (bond quotes do not include accrued interest), but that's still an annualized yield of about 19% according to your link.

When a bond sells for below par, it means that it pays an interest rate lower than the equivalent rate for other bonds of equivalent risk. Since this bond pays a decent interest rate, a price 6% below par means that the market thinks there is a significant risk of default in the next 5 months. So there's a chance you'll get less than the full face value, and a very small chance you'll end up with nothing.

Given that the company is in the catering business during a global pandemic, it may just be market sentiment towards the industry itself, and not something specific to this bond, but there's not anything obvious either way.

Just like individual stocks, individual bonds can carry significant risks specific to that company. You'll most likely get the yield promised by the price, but if you're not willing to take the risk of larger losses, then stay away (i.e. don't bet the family mortgage or your entire retirement plan on it).

As a general rule, when you look at the price of a publicly tradeable security, assume it is fairly priced. If a market is reasonably efficient, then any public information about the underlying company or commodity is incorporated into how professional traders feel about the future profitability of that thing. You could argue that this isn't always the case - for example, maybe TSLA is overpriced because 'the market' is too optimistic about the future government approval of Full Self Driving. But there will be other people who agree with you about that, and are also trading accordingly. Maybe if that wasn't a risk, TSLA would be double the price right now.

So if you assume everything is fairly priced, why is the bond you're looking at so attractive? Risk. Some people want a 'sure thing', and get a government bond paying 1%. Some people are okay with a 2% chance that they lose their investment, and so they are happy to take an extra 4% return. The point is that if you are in a position to accept risk, then you can get higher (on average) returns for it, because volatility is a bad thing, that people will pay to get rid of. The higher the premium you would receive for taking someone's risk, the bigger the warning - in the case of your bond link, this is a sign that the market strongly dislike's the risk associated with the chance of getting full repayment.