It's an unfortunate use of term, because while fizzy does mean bubbly and frothy, it can also mean unsustainable because the fizz in drinks never lasts. Author

It's an unfortunate use of term, because while fizzy does mean bubbly and frothy, it can also mean unsustainable because the fizz in drinks never lasts. Author should have / could have used the title "Tech Investors can't get enough of Europe's growing startup scene". Would have conveyed a much less bubbly / frothy / transient nature.